In fuel dispensing apparatus of the type described, a valve shutoff system conventionally is provided upstream of the fuel delivery hose and such that when the valve shutoff system is opened to activate the apparatus for dispensing fuel, fuel is thereupon supplied under pressure to the fuel delivery hose. If the hose pressure had been relieved at the end or after the immediately preceding fuel delivery by opening the usual dispensing nozzle valve after the valve shutoff system is closed, the flexible hose is expanded or dilated slightly by the fuel under pressure supplied to the hose when the apparatus is reactivated for the succeeding delivery. As a result, there is a small volume of fuel flow to the hose even before any fuel is manually dispensed from the nozzle. Also, that small amount of fuel flow is displayed by the usual register conventionally provided for displaying the volume and cost amounts of fuel delivered. Thus, although the volume amount of fuel resulting from hose dilation may be relatively small, because of the existing high and expected even higher unit volume price of gasoline, the corresponding cost amount of fuel may be two or three cents or more. As a result, the cost registration system appears inaccurate, and objections may be raised by the fuel customers.
Prior art systems have been devised which provide a shutoff valve downstream of the hose to maintain the hose pressurized between fuel deliveries and so that when the downstream shutoff valve is opened to activate the system for dispensing fuel, the volume and cost registers remain at zero until fuel is actually dispensed.
Werder U.S. Pat. No. 1,929,719; Healy U.S. Pat. No. 3,823,751; Mackie U.S. Pat. No. 3,254,795; and Jones, Jr. et al. U.S. Pat. No. 3,138,289 disclose fuel dispensing systems having a shutoff valve downstream of the hose for deactivating the system after a preset amount of fuel is dispensed. However, such prior art systems have not been extensively used if at all because of their impractical design and because they fail to comply with the strict regulations dealing with the safety and accuracy of fuel dispensing apparatus. For example, such prior art systems do not provide for accurately terminating the fuel delivery after a preset volume or cost amount is dispensed. Also, electrically operated valve shutoff systems which employ a solenoid operated shutoff valve at the nozzle present very serious safety problems and must be designed to avoid electrical fire hazards and therefore are generally considered impractical.